21天学习android开发教程之SurfaceView

上一篇文章介绍了MediaPlayer相关内容，这次用两篇文章来介绍SurfaceView的用法。网上介绍SurfaceView的用法有很多，写法也层出不同，例如继承SurfaceView类，或者继承SurfaceHolder.Callback类等，这个可以根据功能实际需要自己选择，我这里就直接在普通的用户界面调用SurfaceHolder的lockCanvas和unlockCanvasAndPost。
先来看看程序运行的截图：

截图1主要演示了直接把正弦波绘画在SurfaceView上 

对比上面的左右两图，右图用.lockCanvas(null)，而左图用.lockCanvas(new Rect(oldX, 0, oldX + length,getWindowManager().getDefaultDisplay().getHeight()))，对比一下两个效果，由于左图是按指定Rect绘画，所以效率会比右图的全控件绘画高些，并且在清屏之后(canvas.drawColor(Color.BLACK))不会留有上次绘画的残留。

接下来贴出main.xml的源码:

接下来贴出程序源码：

package com.testSurfaceView;

import java.util.Timer;
import java.util.TimerTask;

import android.app.Activity;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.os.Bundle;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.widget.Button;

public class testSurfaceView extends Activity {
    
    Button btnSimpleDraw, btnTimerDraw;
    SurfaceView sfv;
    SurfaceHolder sfh;

    private Timer mTimer;
    private MyTimerTask mTimerTask;
    int Y_axis[],//保存正弦波的Y轴上的点
    centerY,//中心线
    oldX,oldY,//上一个XY点 
    currentX;//当前绘制到的X轴上的点

    @Override
    public void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.main);

 btnSimpleDraw = (Button) this.findViewById(R.id.Button01);
 btnTimerDraw = (Button) this.findViewById(R.id.Button02);
 btnSimpleDraw.setonClickListener(new ClickEvent());
 btnTimerDraw.setonClickListener(new ClickEvent());
 sfv = (SurfaceView) this.findViewById(R.id.SurfaceView01);
 sfh = sfv.getHolder();

 //动态绘制正弦波的定时器
 mTimer = new Timer();
 mTimerTask = new MyTimerTask();

 // 初始化y轴数据
 centerY = (getWindowManager().getDefaultDisplay().getHeight() - sfv
  .getTop()) / 2;
 Y_axis = new int[getWindowManager().getDefaultDisplay().getWidth()];
 for (int i = 1; i < Y_axis.length; i++) {// 计算正弦波
     Y_axis[i - 1] = centerY
      - (int) (100 * Math.sin(i * 2 * Math.PI / 180));
 }
    }

    class ClickEvent implements View.onClickListener {

 @Override
 public void onClick(View v) {

     if (v == btnSimpleDraw) {
  SimpleDraw(Y_axis.length-1);//直接绘制正弦波
     
     } else if (v == btnTimerDraw) {
  oldY = centerY;
  mTimer.schedule(mTimerTask, 0, 5);//动态绘制正弦波
     }

 }

    }

    class MyTimerTask extends TimerTask {
 @Override
 public void run() {

     SimpleDraw(currentX);
     currentX++;//往前进
     if (currentX == Y_axis.length - 1) {//如果到了终点，则清屏重来
  ClearDraw();
  currentX = 0;
  oldY = centerY;
     }
 }

    }
    
    
    void SimpleDraw(int length) {
 if (length == 0)
     oldX = 0;
 Canvas canvas = sfh.lockCanvas(new Rect(oldX, 0, oldX + length,
  getWindowManager().getDefaultDisplay().getHeight()));// 关键:获取画布
 Log.i("Canvas:",
  String.valueOf(oldX) + "," + String.valueOf(oldX + length));

 Paint mPaint = new Paint();
 mPaint.setColor(Color.GREEN);// 画笔为绿色
 mPaint.setStrokeWidth(2);// 设置画笔粗细

 int y;
 for (int i = oldX + 1; i < length; i++) {// 绘画正弦波
     y = Y_axis[i - 1];
     canvas.drawLine(oldX, oldY, i, y, mPaint);
     oldX = i;
     oldY = y;
 }
 sfh.unlockCanvasAndPost(canvas);// 解锁画布，提交画好的图像
    }

    void ClearDraw() {
 Canvas canvas = sfh.lockCanvas(null);
 canvas.drawColor(Color.BLACK);// 清除画布
 sfh.unlockCanvasAndPost(canvas);

    }
}

以上就是本文的全部内容，希望对大家学习Android软件编程有所帮助。